The present invention was developed with the issues associated with using one hydraulic pump to drive multiple devices. While this appears to be simply resolved by splitting a pump's output line into several, so that there is one line feeding each device, the actual solution is not so simple. In an ideal situation where each device was perfectly identical, and the load on each device was equal and constant, this might work. However, in real and practical terms it is impossible for two identical devices to be actually identical in every way (or to remain so due to wear, etc.). Similarly it is rare for loads to remain constant and equal on each circuit. There is also the situation that the user may wish to drive different types of devices off the same pump.
One solution used in the art is to use a ‘flow divider’, which is a pressure compensated flow control valve which typically splits an input flow into two output flows. The output flows can be set up to be equal, or to differ from each other by a predetermined ratio. However, there are problems associated with these devices. For instance they tend to operate to maintain flow control within a narrow range, rather than at one particular predetermined point. Hence they are only useful where variations within a range of limits (depending on the device in a particular situation) is acceptable.
Where a higher degree of control is required, a rotary flow divider is used. This comprises a linked series of hydraulic motors fed from a common input. There is no load on each of the hydraulic motors, and there is one motor for each required output. It is assumed that the flow of hydraulic fluid through each (identical) motor rotating at the same speed (which they must be because they are linked) is identical. Hence on the output side of each motor is an equal flow of hydraulic fluid.
While effective in many situations, rotary flow dividers suffer one particular problem—intensification. Assume there are a plurality of motors in the rotary flow divider each feeding a device under load. Now assume that the load on one (or more) of the devices attached to a motor reduces or drops to zero. The full differential hydraulic pressure will then be applied to the other motors. What then happens is that these motors start acting as pumps and drive their connected devices much harder than they should. The rotary flow divider then fails as a device for equally distributing a hydraulic output to multiple circuits.
Another disadvantage of the rotary flow divider, apart from the need for one motor for each circuit, is that they are generally unsuitable for low fluid flow rates. Rotary flow dividers typically work best at around 1500 rpm minimum. Given that the typical minimum size of available hydraulic motors (suitable for use therein) is around 1 cc (cubic centimetre) we have a minimum flow rate of around 1.5 liters/minute per circuit, which is too high for many applications.
Accordingly there is a need to provide an improved device for predictably dividing a fluid output, such as a hydraulic output, into several circuits.
Accordingly, it is an object of the present invention to address the above problems.
It is a further object of the present invention to provide flow dividing apparatus suitable for use in a hydraulic circuit.
At the very least it is an object of the present invention to provide the public with a useful alternative choice.
Aspects of the present invention will be described by way of example only and with reference to the ensuing description.